This study examines the effect of the frequency of modulated water jet on material erosion in both air and submerged environments. Two prototypes of nozzles with the ability to self-excite flow oscillations, each featuring an identical outlet orifice (1x1 mm), were developed to modulate water jets at distinct oscillating frequency levels (from 6 to 45 kHz). Jet oscillation characteristics were predicted via computational fluid dynamics (CFD) and validated experimentally using direct pressure-sensor measurements and indirect optical frequency-monitoring techniques. Optimal standoff distance (SOD) between the selected nozzle and the target surface was found (from 10 to 15 mm). Erosion tests were conducted on pure copper samples in both air and underwater conditions. During erosion testing, flow rates (19 and 24 l/min) and pressures (80 and 140 MPa) were continuously recorded by diagnostic sensors to maintain constant hydraulic power (26 kW and 55 kW). The resulting erosion grooves formed on copper samples under air and submerged conditions by moving the nozzle above the target surface (1 mm/s) were characterized by optical profilometry and scanning electron microscopy (SEM). Quantitative analysis of removed volume, groove geometry, and surface defects was conducted to elucidate the relationship between the frequency of the modulated water jet and erosion performance. The results confirmed that an increase in the frequency of the modulated high-speed water jet significantly enhances erosion efficiency in both tested environments. However, in submerged conditions, a pronounced attenuation of the jet occurs, reflected in a lower volume of material removal. Further details are discussed in the subsequent sections of the manuscript.

Microscopic rock image analysis aids geotechnical and geological studies, often with computational methods. The growing availability of image data has led to the widespread adoption of automation in image analysis. However, the lack of large, publicly available datasets has hindered the development of dedicated machine learning models for geological applications. This study explores the use of transfer learning techniques to overcome this limitation by leveraging pre-trained machine learning models for rock type classification based on thin-section images. The research compares models trained from scratch with those utilizing pre-trained architectures to assess whether models trained on non-geological data can effectively support rock classification. The experiments were conducted using a dataset comprising 11901 microscopic images representing 40 rock types. The study evaluates different model initialization methods to assess their performance in geological applications. The results indicate that transfer learning enhances classification accuracy compared to models trained from scratch, demonstrating the potential in geoscientific research. This work provides insights into the practical application of machine learning in rock classification and serves as a reference and survey for specialists in geotechnics and geology seeking to integrate artificial intelligence into their research.

Topazolite (greisen) is a rock formed essential by quartz and topaz, with accessory white mica, tourmaline, sulphides (molybdenite and arsenopyrite), wolframite and cassiterite. This rock was found in the Krkonoše and Jizera Mountains in the western Sudetes. In Poland, this metasomatic rock occurs at the contact between leucogranite and mica schist (associated with hydrothermal kaolinization) in a narrow zone between the settlements of Rebiszow and Gierałtówek. On Czech territory, similar topaz quartzolite (greisen rock), consisting of up to 65 % quartz and 32 % topaz, was found near the settlements of Růžek and Vítkov near Chrastava in association with orthogneiss. The high content of topaz in this rock offers the possibility of using it as an abrasive in high-speed abrasive water jet technology for cutting and surface treatment of hard metallic and non-metallic materials. In the crushed form, after being concentrated in a treatment plant, topaz could be a natural abrasive with a wide range of applications. However, the results of technological testing of the physical and mineralogical characteristics of the topaz concentrate indicate its unfavorable properties caused by the high fissility of topaz. This leads to losses of topaz during its technological adjustment to the required grain size or during recycling. It has been shown that abrasive concentrates with topaz content above 90 % are promising, especially for special applications of abrasive water jet technology. Mastering the technology for processing of the source raw material, i.e. topaz quartzolite, into a topaz-rich concentrate, and subsequent applied research on the use of topaz abrasives in industry are crucial.

Rocks with an enrichment of topaz (quartz-topaz quartzolites) found in the Krkonoše-Jizera crystalline complex in northern Bohemia or a potential secondary raw material from the mining of cast mica from greisen (Czechia) can be a suitable raw material for obtaining topaz concentrate for its subsequent use in Abrasive Water Jet (AWJ) technology as an abrasive. Topaz from these rocks has good mineralogical parameters, density and hardness. The grains of the topaz concentrate are also less fractured. This article outlines the basic properties of topaz in relation to its use as a potential abrasive for AWJ, including basic testing of its cutting abilities compared to other abrasive concentrates. The cutting performance of topaz was found to achieve 90.5

This paper investigates the erosive wear of focusing tubes in abrasive water jet (AWJ) cutting processes, in particular the effect of physical vapor deposition (PVD) coating on the tube durability. Through controlled experiments, the wear rates of focusing tubes coated with different PVD multi-coatings are analyzed and compared with uncoated tubes. Initial results show that PVD coatings exhibit higher wear rates in the early stages due to their brittle nature, however they stabilize and ultimately enhance the overall lifetime of the focusing tubes. This study provides valuable insights into the mechanisms of wear and the effectiveness of PVD coatings in the operational life extension of focusing tubes, and also suggests potential improvements in coating techniques to optimize the tube performance.

Rock and gas outburst is one of the most significant natural hazards faced by the mining industry. In the last decade, this issue has appeared in firm rock mining (including copper ore mines) in addition to coal mining. A number of methods have been developed for coal mining to assess the hazard posed by gasogeodynamic phenomena, but in the case of copper ore mines, no studies have led to forecasts of this risk. To face the challenge, the authors decided to propose their own concept of risk assessment principles based on a threshold analysis of the phenomenon and a continuous analysis using fuzzy logic. A series of tests were performed to support the paper, investigating selected parameters which directly affect the risk. The evaluation principles for gasogeodynamic phenomena presented herein were the result of experimental investigations carried out by the authors.

The paper focuses on the resistance of rocks to fast-flowing liquids using a well-established method of accelerated hydro-abrasive-cavitation simulation based on special application of abrasive water jets. Erosion resistance was tested on large samples of nine rock types from various quarries in Czechia (granite, gneiss, basalt, granodiorites, metabasites and marbles). New surfaces created after the application of simulative erosion flows were analysed and their texture was described. Relationships between the erosion resistance of rocks and their selected properties (i.e. compression and flexural tensile strengths, abrasiveness and abrasivity) were studied. It has been found that erosion resistance of rocks tested on the hydro-abrasive erosion differs significantly and is closely related to the mineral composition and internal rock structure. Basalt was proved to be the most resistant, followed by metabasites, fine-grained Litice Granodiorite, coarse-grained granite, gneiss, both marbles and fine-grained Silesian Granodiorite. No relationship was found between the observed properties of rocks and their resistance to the accelerated hydro-abrasive-cavitation erosion. The method developed by the authors is unique, enabling quick analysis of erosion resistance of various materials to fast-flowing liquids. The paper provides with new knowledge on behaviour and resistance of rock interacting with fast-flowing liquids related to their structure and properties, which has not been studied so far.

There are many technological ways to activate biocompatible surfaces, but in some cases, there are not reliable for elderly patients. It has been found that surfaces created using pulsating water jets have a structure similar to trabecular bone structures. Such a similar shape to the endoprosthesis stems would enable faster fixation. The paper presents a novel way of utilizing the water hammer effect caused by forced multiple droplet impingement with a spatial frequency of 40,000 i/s on Ti6Al4V titanium alloy surface under different technological conditions. The objective was to create a structured surface with desired values of surface profile parameters Ra and Rz to increase the possible potential for implant osseointegration, fixation and stability. Pulsating water jet was generated at pressures from 20 to 100 MPa using a circular nozzle with a diameter of 1.32 mm. Two different strategies of the jet trajectory, namely linear and cross-hatch strategy, were investigated. Results were compared with grit blasted followed by plasma spray-coated femoral stem for cementless total hip arthroplasty. It has been found that variation in the input parameters results in significant changes in the surface generated. Samples whose surfaces were generated using energy intensity lower than 5 KJ/mm 2 and have surface roughness in the range Ra = 4 – 8 μm were selected for surface topography and morphology analysis along with the commercial femoral stem. SEM analysis revealed the absence of foreign contamination and steeper surface heights on pulsating water jet treated samples compared to standard femoral prosthetic. The cross-section images showed the presence of sub-surface voids and craters of different sizes due to the jet's action. Surface topology is similar to trabecular shape. This indicates that roughening the surface increases the surface area and thus has potential bone tissue ingrowth during osseointegration.

This paper deals with investigation of conditions of formation, propagation and decay of a flat water jet after it exits a nozzle at water pressures of 10 and 20 MPa. The water jets were visualized with shadowgraphs and the dimensions of water clumps and droplets at different distances from the nozzle outlet were studied. During the optical measurements, the flow and pressures in the high-pressure area of the water circuit were monitored. The magnitude of the incident pressure at the centre of the jet was also measured. It was observed that the used optical equipment breakdown into fine structures occurred mainly at greater distances from the nozzle. A linear relationship between the number of small droplets and the distance from the nozzle was observed. The magnitude of the impact pressure decreased with increasing SODs according to an exponential relationship.

This paper deals with visualization and geometrical analysis of flat water jet structures. The shadowgraphy method created by a CCD camera and high-energy pulsed laser, as well as the image analysis method were tested. The jet structures were captured in the centre of axis symmetry. The influence of water pressures on water clusters dimensions and droplets was studied. The designed diagnostic water line consisting of a pressure sensor and a turbine flowmeter was used for flow monitoring during experimental flow visualization. The impact pressures of impinging water clusters and droplets were measured in centre of the jet. The experimental tests were performed in the following range of operating conditions: water pressure up to 20 MPa at maximal flow rate of 39 l/min and hydraulic power of 13.32 kW. A linear relationship between the number of small droplets and the distance from the nozzle was analysed.

Rock and gas outbursts occur most frequently in coal mining. Gas-induced geodynamic events in dolomite are a new and unexplored phenomenon. In the last time, two outbursts of gas and dolomite have occurred in the Legnica-Głogów Copper Region in southwestern Poland, which is one of the world’s largest copper ore mining regions. Gas-induced geodynamic events are dependent on the co-occurrence of two factors: rock porosity, and the presence of gas under significant pressure in the pores and crevices of the rock. This paper presents a condensed energy balance for the phenomenon of outbursts of dolomites and gases. The quantity of energy depends on the type of transformation taking place during decompression. The work produced enables first the disintegration of the rock, and then its transportation along the mine working space. This paper has focused on the estimation of the energy required to disintegrate the rock. It has been estimated that 0.38 MJ is needed for the size reduction of 1 m3 of ejected mass.

It is generally known that the properties of concrete, particularly the strength, vary depending on the concrete age due to the chemical-mechanical processes occurring in the structure of concrete during ageing (maturing). The issue often is the time needed for concrete to reach its desired safety before a concrete structure made of fresh concrete can be partially or completely loaded. In structures coming into contact with flowing liquids, the resistance of surface layers to erosion caused by abrasion or cavitation is also important, in addition to the strength. Therefore the analysis of effects of the concrete age from 7 days to 1 year on the concrete resistance to fast-flowing liquids is the subject of this paper. A method of accelerated hydraulic-mechanical simulation of the surface layer loading by means of a pure high-speed water jet and a water jet with abrasive particles was used in order to investigate the concrete erosion resistance. The influence of the concrete age on the resistance to fast-flowing liquids has been proven. After a year, the concrete resistance increased by about 36% in the case of the pure water jet, and 28% in the case of the abrasive water jet.

The article studies the process of drilling with an Injection Abrasive Water Jet (IAWJ). Two different aluminium-based materials with various properties were chosen as test specimens for drilling: (i) very hard and abrasion-resistant alumina ceramics and (ii) soft and easy-to-machine aluminium alloy. The development of drilled holes was observed as a function of the exposure time of the jet acting on a drilled material surface. The exposure time was varying from 0.1 s to 102.4 s. The inlet diameter of the drilled hole, hole depth, volume of material removed from the hole and hole shape were continuously observed. It has been found that the drilled holes differ significantly depending on the type of material. While the soft aluminium alloy can be drilled easily and the hole was drilled through the material in a short time (20 mm thick sample in 24 s), the drilling process was significantly slowed down due to the strength and abrasion resistance of ceramics (12.7 mm deep hole in 102.4 s). The drilled hole shape is flatter in ceramics than in aluminium alloys.

The presented article is focused on the evaluation of mechanical properties of stainless steel disintegrated using an ultrasonically modulated pulsating water jet. The experimental procedure was performed using a nozzle with a circular orifice with an equivalent diameter of 1.6 mm. The mechanical properties evaluation was based on indentation elasticity modulus Ep and nano hardness H, which were measured using nanoindentation technique. Influence of ultrasonic power and plunger pressure change on disintegrated material was evaluated. Changes in mechanical properties in dependence on distance from the disintegrated surface were evaluated. Elasticity modulus and nano hardness change were observed below and on the sides of the disintegrated surfaces. Measurements were performed until the distance of 930 μm. The indentation was carried in three series of 10 indents with 100 μm spacing located below the affected area, next to the affected area and in the unaffected material. Results of experimental testing show changes of nano hardness (generally an appreciable decrease) and elasticity modulus (limited increase) of material under and to the side of the newly created surface.

Virtually every concrete structure comes into contact with abrasive effects of flowing media or solids, which have a direct impact on the durability of concrete. An abrasive effect is most pronounced in transport or water management structures, and these structures are often designed for a significantly longer service life (usually 100 years). This research evaluates the influence of the filler component in terms of the type of aggregate and its mineralogical composition on concrete abrasion resistance. As part of the impact of the binder component, several concrete mixtures were produced using the same aggregate and maintaining the same strength class with the addition of different types of active and inert mineral additives. In other parts of the research, the effect of adding fiber reinforcement on the abrasion resistance of concrete was verified. Mutual connections and correlations in different age groups (7, 28 and 90 days) were sought for all obtained results. The abrasion resistance of the composite was monitored by using standard procedures, especially using a Böhm device. It was found that for good abrasion resistance of concrete, it is not necessary to produce concretes with high strength classes using often expensive mineral additives (microsilica) and quality aggregates, but the maturation time of the composite and its microstructure plays an important role.

Abrasives are an integral part of the abrasive water jet (AWJ) technology and have a significant impact on the efficiency and economy of the cutting process. The abrasive particles are accelerated by the water jet and transported to the point of their interaction with the cut material. There are many factors influencing the determination of the abrasive type to be used in the AWJ process. In this study, series of experiments were performed with the aim to evaluate the erosion performance of abrasive particles in an abrasive water jet cutting process. Three types of abrasives were used in the process of cutting of several types of materials by the abrasive water jet. The wear of a focusing tube due to the action of abrasive particles during their acceleration was also evaluated. The paper presents a methodology for evaluation of abrasives with respect to their use in the abrasive water jet cutting process.

This article deals with the evaluation of surface topography created by Abrasive Water Jet (AWJ) technology. The effects of machining parameters on the turned surface was analyzed by roughness parameters. Further attention is paid to the influence of technological factors on the surface quality created by abrasive water jet turning processes. Based on an input and output system, a database design was created providing the evaluation of the surface quality. Various materials were used for the database which should serve to optimize the abrasive water jet turning processes in order to increase the technological efficiency and contribute to its automation.

Printed circuit boards are part of electronic devices and affect the functioning of today's society. At present, printed circuit boards are manufactured for relatively long periods of time using the same methods. The presented article focuses on the design of the possibility which eliminates errors arising from the development and etching of PCBs. It describes the theoretical design of the use of hydrodynamic continuous water jet machining in PCB production. The proposal points to the possibility of using positive water jet properties are as such: no heat-affected zone, thin separation gap, absence of dust particles and toxic fumes.

The paper deals with the use of the abrasive water flow technology in an accelerated simulation of the process of mechanical degradation of surface layers of cement-based composites by flowing liquids. Effects of the abrasive particle size and the mass flow rate of abrasives in an abrasive water flow impacting on the surface of concrete samples have been studied. In addition, suitability of the application of the abrasive water flow for the simulation of real situation of the surface wear by flowing liquids has been evaluated.

Abstract Concrete structures affected for a long time by flowing liquids are exposed to gradual erosion in surface layers caused by a combination of several degradation processes: abrasion, cavitation and chemical or bacterial impacts. Due to the complex phenomena and difficult-to-define initial and boundary conditions, the whole process cannot be easily simulated using the conventional computing tools. Laboratory experimental research is thus the most appropriate approach for the investigation of a suitable composition of concrete resistant to the flowing liquids. However, the methods used are often very time consuming and last even several years. High-speed water flows can be elegantly used for the acceleration of the mechanical simulation of a real situation. Several experiments on the effects of the high-speed water flows on concrete surfaces have been carried out. Using the X-Ray CT methods, subsurface structures of concretes exposed to the accelerated mechanical simulation of the erosion wear caused by fast flowing liquids were investigated and presented in the article. It has been shown that the simulation does not cause initiation of new fractures or cracks in the original concrete structure. The pure water flow mainly removes the hardened cement paste and reveals the aggregate grains. The water flow with abrasive particles disintegrates in greater depths and washes out entire aggregate grains, eventually amputates them and finally smoothens entire surface.